1. Technical Field
This invention relates generally to molded gaskets, and more particularly to those designed to be received into a channel and molded with side retaining features that frictionally engage and hold the gasket within the channel.
2. Related Art
Injection molded gaskets fabricated of rubber and the like (such as NBR) are known for installation within a channel of a cover component or the like (e.g., a front cover of an engine). The top and bottom margins of the gasket present longitudinally extending seal surfaces that seal against the bottom wall of the channel and a facing surface of a mating component, respectively, to which the cover is to be mounted.
During manufacturing and servicing of the engine, it is desirable to firmly support the gasket within the channel while the cover is separated from the mating component to prevent unintended loss or misalignment of the gasket. In one known gasket construction, the gasket has molded retaining features in the form of a plurality of longitudinally spaced nubs or bump-like buttons that project laterally outwardly of the gasket on its opposite sides. The nubs extend a predetermined distance laterally outwardly from the body of the gasket, such that the tips of the nubs lay along a tip line on opposite sides of the gasket. The lateral spacing between the opposing tip lines is slightly greater than the width of the channel so that the nubs elastically deform and compress against the walls of the channel upon pressing the gasket into the channel.
One problem that the present inventors have discovered when working with such injection molded gaskets concerns the placement of the ingates of the mold tooling relative to the gasket. At least one, and typically several ingates are provided in the tooling for injecting the hot flowing gasket material into the die cavity. When the material cools, the material that remains in the ingates must be trimmed free of the gasket. What the inventors have found through development work is that while it is preferable to locate the ingates along the tip line of the nubs (which also lies in the central parting plane of the mold tooling), it is difficult at best to trim the ingate material following molding in a way that does not extend the gasket material beyond the tip line. This is particularly a problem when the ingates are required to be large enough to extend longitudinally across, and thus bridge, two or more adjacent retention nubs. With a tough material like NBR, for example, trimming the ingate material by conventional means still leaves a thick, wide, and relatively less flexible xe2x80x9cribxe2x80x9d projection that decreases the flexibility of the affected nubs and causes the gasket to roll and misalign in the area of the ribs when the gasket is pressed into the channel.
It is an object of the present invention to overcome or minimize the foregoing limitations associated with molded gaskets.
An injection molded gasket constructed according to a presently preferred embodiment of the invention has a longitudinally extending gasket body with laterally opposite sides and a plurality of longitudinally spaced retention nubs projecting laterally outwardly of the body from the opposite sides. At least one longitudinally extending ingate rib is formed on the gasket body and bridges at least two adjacent ones of the retention nubs. The ingate rib has a trimmed edge that extends no further outwardly of the body than do the retention nubs located adjacent those nubs bridged by the ingate rib.
The invention further contemplates a method of injection molding gaskets in which at least one material ingate rib is formed on the gasket bridging at least two longitudinally adjacent retention nubs. The bridged nubs are formed and the ingate rib trimmed in such manner that a trimmed edge of the rib extends no further outwardly of the gasket body than do retention ribs located adjacent the bridged nubs.
The invention has the advantage of incorporating the ingate material into the gasket in such manner that it serves and can function as a retaining feature with the other retaining nubs.